sustaining terrestrial biodiversity: saving...

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LIVING IN THE ENVIRONMENT, 18e G. TYLER MILLER • SCOTT E. SPOOLMAN

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10 Sustaining Terrestrial

Biodiversity: Saving Ecosystems

and Ecosystem Services

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• Suffered widespread deforestation

• Still harbors great biodiversity

– Microclimates provide variety of habitats

– More than 25% of its land is nature reserves

and national parks

• Government pays landowners to restore

forests

Core Case Study: Costa Rica – A Global

Conservation Leader

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Fig. 10-1, p. 218

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• Forest ecosystems provide ecosystem

services far greater in value than the value

of raw materials obtained from forests

• Chief threats to forest ecosystems

– Unsustainable cutting and burning of forests

– Diseases and insects

– Projected climate change

10-1 What Are the Major Threats to Forest

Ecosystems?

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• Old-growth or primary forest (about 36%)

– Uncut not disturbed for several hundred years

– Reservoirs of biodiversity

• Second-growth forest

– Secondary ecological succession

• Tree plantation (tree farm, commercial

forest)

– May supply most industrial wood in the future

Forests Vary in Their Age, Make-Up, and

Origins

Fig. 10-2, p. 219

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Fig. 10-3a, p. 219

25 yrs Weak trees

removed

Clear cut

30 yrs

Years of growth 15 yrs

Seedlings

planted

5 yrs 10 yrs

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Fig. 10-3b, p. 219

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• Store atmospheric carbon

• Provide habitats

• Influence local and regional climate

• Provide raw materials

• Provide health benefits

– Medicines derived from plant species

Forests Provide Important Economic and

Ecosystem Services

Fig. 10-4, p. 220

Forests

Support energy flow

and chemical cycling

Fuelwood

Ecological

Services

Economic

Services

Natural Capital

Reduce soil erosion Lumber

Absorb and release

water Pulp to make

paper

Purify water and air Mining

Influence local and

regional climate Livestock

grazing

Store atmospheric

carbon Recreation

Provide numerous

wildlife habitats Jobs

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• One of the world’s largest industries

• Selective cutting

– Intermediate-age or mature trees are cut

singly or in small groups

• Clear-cutting

– All trees in an area are removed

• Strip cutting

– Clear-cutting in strips

There Are Several Ways to Harvest Trees

New highway

Old growth

Cleared plots for agriculture

Highway

Cleared plots for grazing

Fig. 10-5, p. 221

Stepped Art

(b) Clear-cutting

Muddy

stream

Uncut

Cut 1 year ago

Dirt road

Cut 3–10 years ago

Uncut

Clear stream

(a) Selective cutting

(c) Strip cutting

Clear stream

Fig. 10-6, p. 222

Fig. 10-7, p. 222

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Fig. 10-8, p. 222

Trade-Offs

Clear-Cutting Forests

Advantages Disadvantages

Higher timber yields Reduces biodiversity

Destroys and

fragments wildlife

habitats

Maximum profits in

shortest time

Can reforest with

fast-growing trees Can lead to water

pollution, flooding,

and erosion, especially

on steep slopes

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• Surface fires

– Usually burn leaf litter and undergrowth

– Provide many ecological benefits

• Crown fires

– Extremely hot – burns whole trees

– Kill wildlife

– Increase soil erosion

Fire, Insects, and Climate Change Can

Threaten Forest Ecosystems

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• Introduction of foreign diseases and

insects

– Accidental or deliberate

• Global warming

– Rising temperatures

– Trees more susceptible to diseases and pests

– Drier forests – more fires

– More greenhouse gases

Fire, Insects, and Climate Change Can

Threaten Forest Ecosystems (cont’d.)

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Fig. 10-9, p. 223

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• Deforestation

– Temporary or permanent removal of large

expanses of forest for agriculture,

settlements, or other uses

– Tropical forests

• Especially in Latin America, Indonesia, and Africa

– Boreal forests

• Especially in Alaska, Canada, Scandinavia, and

Russia

Almost Half of the World’s Forests Have

Been Cut Down

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Fig. 10-11, p. 224

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• Majority of loss since 1950

– Mostly in Africa, Southeast Asia, South

America

– Clearing trees can accelerate climate change

• Drier climate

– Risk of larger and more frequent forest fires

• Ecological tipping point

– Forest cannot grow back

Tropical Forests are Disappearing Rapidly

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Fig. 10-15, p. 225

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• Various causes

– Population growth

– Poverty of subsistence farmers

– Ranching

– Lumber

– Plantation farms – palm oil

• Begins with building of roads

• Many forests burned

Causes of Tropical Deforestation Are

Varied and Complex

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• We can sustain forests by:

– Emphasizing the economic value of their

ecosystem services

– Removing government subsidies that hasten

their destruction

– Protecting old-growth forests

– Harvesting trees no faster than they are

replenished

– Planting trees

10-2 How Should We Manage and

Sustain Forests?

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• Certify sustainably produced forest

products

• Use more sustainable logging practices in

tropical forests

• Phase out government subsidies

We Can Manage Forests More Sustainably

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• Improve the efficiency of wood use

– 60% of U.S. wood use is wasted

• Make tree-free paper

– Kenaf

We Can Reduce the Demand for

Harvested Trees

Solutions: Fast-Growing Plant: Kenaf

Fig. 10-17, p. 228

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• Debt-for-nature swaps/conservation

concessions

– Protect forests in return for aid

• Crack down on logging

• End subsidies

• Plant trees

There Are Several Ways to Reduce

Tropical Deforestation

Fig. 10-19, p. 230

Solutions

Sustaining Tropical Forests

Prevention Restoration

Protect the most

diverse and

endangered areas

Encourage

regrowth through

secondary

succession Educate settlers

about sustainable

agriculture and

forestry

Subsidize only

sustainable forest use

Rehabilitate

degraded areas

Protect forests through

debt-for-nature swaps

and conservation

concessions

Certify sustainably

grown timber

Concentrate

farming and

ranching in

already-cleared

areas Reduce poverty

and slow

population growth

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• We can sustain the productivity of

grasslands by:

– Controlling the numbers and distribution of

grazing livestock

– Restoring degraded grasslands

10-3 How Should We Manage and

Sustain Grasslands?

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• Rangelands

– Unfenced grasslands in temperate and

tropical climates that provide forage for

animals

• Pastures

– Managed grasslands and fences meadows

used for grazing livestock

Some Rangelands Are Overgrazed

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• Overgrazing of rangelands

– Reduces grass cover

– Leads to erosion of soil by water and wind

– Soil becomes compacted

– Enhances invasion of plant species that cattle

won’t eat

Some Rangelands are Overgrazed

(cont’d.)

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Fig. 10-22, p. 231

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• Rotational grazing

– Cattle moved around

• Fence damaged areas

• Suppress growth of unwanted plants

– Herbicides

– Controlled burning

We Can Manage Rangelands More

Sustainably

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Fig. 10-23, p. 232

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• Sustaining biodiversity will require:

– More effective protection of existing parks and

nature reserves

– The protection of much more of the earth’s

remaining undisturbed land area

10-4 How Should We Manage and Sustain

Parks and Natural Reserves?

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• Worldwide – 6600 national parks

• Parks in developing countries

– Greatest biodiversity

– 1% protected against illegal:

• Animal poaching

• Logging and mining

National Parks Face Many Environmental

Threats

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• There are 58 major national parks in the

U.S.

• The biggest problem may be popularity

• Other problems include:

– Nonnative species

– Poaching

– Commercial development

– Park maintenance

Case Study: Stresses on U.S. Public Parks

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• Currently less than 13% is protected

• Conservationists’ goal – protect 20%

• Size and design of protected area is

important

– Buffer zone

– Habitat corridor

Nature Reserves Occupy Only a Small

Part of the Earth’s Land

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• Megareserves – large conservation areas

– Designed to sustain about 80% of the

country’s biodiversity

• Large eco-tourism industry

Case Study: Identifying and Protecting

Biodiversity in Costa Rica

Fig. 10-25, p. 236

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• Wilderness

– Land officially designated as having no

serious disturbance from human activities

– Wilderness Act of 1964

• 5% of U.S. land protected as wilderness

• Why is wilderness protection being eroded

today?

Protecting Wilderness Is an Important Way

to Preserve Biodiversity

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Fig. 10-27, p. 237

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• We can help to sustain terrestrial

biodiversity by:

– Identifying and protecting severely threatened

areas (biodiversity hotspots), sustaining

ecosystem services

– Restoring damaged ecosystems (using

restoration ecology)

– Sharing with other species much of the land

we dominate (using reconciliation ecology)

10-5 What is the Ecosystem Approach

to Sustaining Terrestrial Biodiversity?

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• Map global ecosystems and identify

species

• Identify resilient and fragile ecosystems

• Protect the most endangered

• Restore as many degraded ecosystems as

possible

• Make development biodiversity friendly

The Ecosystems Approach: A Five-Point

Strategy

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• 34 biodiversity hot spots are rich in plant

species

– 2% of earth’s surface, but 50% of flowering

plant species and 42% of terrestrial

vertebrates

– 1.2 billion people

Protecting Global Biodiversity Hot Spots Is

an Urgent Priority

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Fig. 10-28, p. 238

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• The world’s fourth largest island

• Roughly 90% of the species found there

are unique

• Severe habitat loss

• Population growth

• Less than 3% of the land area is officially

protected

Case Study: Madagascar: An Endangered

Center of Biodiversity

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Fig. 10-29, p. 239

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• Ecological restoration

– Repairing damage

– Succession processes

• Restoration

• Rehabilitation

• Replacement

• Creating artificial ecosystems

We Can Rehabilitate and Partially Restore

Ecosystems That We Have Damaged

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• Carrying out rehabilitation

– Identify what caused the degradation

– Stop the abuse

– Reintroduce species, if possible

– Protect from further degradation

We Can Rehabilitate and Partially Restore

Ecosystems (cont’d.)